Generally, electroplating processes involve lowering a workpiece or part into a plating bath containing a plating solution. The workpiece or part may be mounted within a loading apparatus, which is configured to be lowered or inserted into the plating bath(s). The part is typically dipped several times in the same bath or several different plating baths. Each time the part is removed from one bath; the part is dipped in a rinsing bath, or a “tack tank” as commonly referred to by one of ordinary skill in the art, to remove excess plating material, prevent oxidation of the part and prepare the part for the next plating bath.
One example of a loading apparatus of the prior art for electroplating processes, and utilized by Pratt & Whitney in East Hartford, Conn., a division of the United Technologies Corporation, is depicted in FIGS. 1-3. The loading apparatus 10 of the prior art is designed to receive a plurality of turbine airfoil blades (not shown).
Loading apparatus 10 has a substantially rectangular container 12 having an inwardly sloping front wall 14, an inwardly sloping back wall 16, a pair of sidewalls 18, 19, a base 20. A bus bar attachment composed of a pair of plastisol stainless steel bus bars 22, 24 is mounted to base 20 underneath each respective receptacle area 30, 31 and between base 20 and another plastisol coated stainless steel bus bar 26. Bus bars 22, 24 are both threadingly secured to bus bar 26 and base 20 by four bolts 28. A round dowel 29, threadingly secured to bus bar 26 by a bolt 27, is designed to connect to a shaft (not shown) of a conveyor apparatus for use in a line for the intended electroplating process. Container 12 includes a pair of receptacles 30, 31, each designed to receive a turbine airfoil blade (not shown). Once the airfoil blades are pneumatically inserted within receptacles 30, 31, a cover 32 is threadingly secured to container 12 by fourteen threaded bolts 34 and two pairs of threaded bolts 42. Each threaded bolt 34 is fitted between a first o-ring 35 and cover 32 within a plurality of first threaded apertures 40 of cover 32, and proximate to both front wall 14 and backwall 16, and sealed with a second o-ring 37. Each threaded-bolt 42 is fitted between a plate 43 and cover 32 within a plurality of second threaded apertures 45 of cover 32, proximate to both first sidewall 18 and second sidewall 19. Each receptacle 30, 31 includes four sidewalls 44, 46, 48 and 50 and a base 52 having an aperture 54. Sidewalls 44, 46 are formed in part by a center portion 33 of cover 32 and a center portion 39 of base 20.
As known to one of ordinary skill in the art, each airfoil blade contains a hollow cavity. In order to prevent plating solutions of one bath from entering the interior cavity of a blade and then contaminating another subsequent bath, the hollow cavities are typically filled with wax. As a result, an operator of the electroplating process must manually fill each airfoil blade's interior cavity. Each turbine airfoil blade is then inserted platform end first into each receptacle 30, 31 using a pneumatic ram or other similar device capable of generating 110 pounds per square inch (psi) to force each airfoil blade into each receptacle 30, 31. Each receptacle 30, 31 requires an airfoil blade in order to prevent transporting electroplating solutions from one bath to another and thus contaminate the baths.
Each airfoil blade must touch the interior base portion within each receptacle 30, 31 in order to receive electrical current from bus bars 22, 24 and 26. When the airfoil blade did not connect in part or completely with the receptacle's interior base portion, the plating would not evenly and/or completely adhere to the blade tip. The resulting unevenly plated airfoil blade would require a quality inspection to determine whether the blade would be scrapped or could be salvaged. In order to salvage an unevenly coated blade tip, the entire cover of the blade must be stripped, the surface cleaned and the airfoil blade reinstalled into loading apparatus 10. This process involves numerous steps which could prevent that particular airfoil blade from being re-plated for over a day or longer. Moreover, if another airfoil blade was not readily available for insertion into the empty receptacle, loading apparatus 10 would be taken off-line in order to prevent the potential contamination of the electroplating baths.
Once the operator has loaded the airfoil blades into receptacles 30, 31, the operator manually aligns cover 32 with the airfoil blades and secures it to container 12. Cover 32 weighs over approximately thirty pounds (30 lbs.) so the operator must be physically capable of lifting, placing and securing cover 32 onto container 12. Once cover 32 is in place, the operator manually inserts and tightens each bolt 34, 42 using a rachet, torque wrench, or other similar tool. Since an air tight seal must be achieved, it was not uncommon for the operator to apply the tool too strongly and accidentally strip a bolt.
At this time, the operator would attach loading apparatus 10 to a mechanized conveyor apparatus (not shown). Upon completion of the process, loading container 12 is detached from the conveyor apparatus and cover 32 is removed. As described earlier, one or more bolts 34, 42 were typically stripped while installing cover 32. In order to remove stripped bolts 34, 42, a maintenance person equipped with a cutting wheel, saw or similar device would cut away each stripped bolt thus requiring additional time and manpower and increasing the cost of plating the airfoil blades. Once bolts 34, 42 were removed, cover 32 was again manually removed by the operator and each blade tip was visually inspected to determine whether or not an acceptable plating was achieved.
The process for coating airfoil blade tips proved to be time consuming, inefficient and cost prohibitive. The tooling costs and additional manpower contributed both time and costs to each run of the production line. The contamination of plating baths also contributed additional time and even temporarily shut down the process to replace a bath and/or tack tank solution. If the operator discovered loading apparatus 10 was carrying excess bath or tack tank solution, then the operator was required to dismantle loading apparatus 10 in order to clean and remove the contaminants. Likewise, if the operator discovered an airfoil became contaminated, then the airfoil blade had to be removed and replaced, if possible, in order to prevent future contamination. Again, the production line would be halted to remove the airfoil blade, and either replace the blade or halt the line if a replacement blade was not available.
In addition to line problems, operators required a pneumatic ram or other device to insert each airfoil blade into receptacles 30, 31. Operators also had to be physically capable of manually lifting, aligning and placing a 30+ lbs. cover 32 onto container 12, and then securing cover 32 to container 12 using a torque wrench, rachet and the like, to tighten eighteen bolts. Inevitably, one or more bolts would be stripped and require a technician or maintenance personnel to cut or saw off the stripped bolt from loading apparatus 10 in order to remove cover 32. Moreover, and even if the production line operated smoothly, there was always a question as to whether all of the airfoil blade tips would be coated properly.
Consequently, there exists a need for an improved loading apparatus designed to receive airfoil blades without the use of a pneumatic tool and capable of maintaining the integrity of its seal to prevent contamination of the airfoils as well as baths and tack tanks.